1. Field of the Invention
The present invention relates to an image pickup apparatus that obtains a two-dimensional light intensity distribution and angle information of a ray in an object space.
2. Description of the Related Art
Recently, an image pickup apparatus that performs a calculation using data obtained by an image pickup element and performs a corresponding digital image processing so as to output various images is proposed. Ren Ng, et al., “Light Field Photography with a Hand-held Plenoptic Camera”, Stanford Tech Report CTSR 2005-2, and Andrew Lumsdaine, et al., “Full Resolution Light Field Rendering”, Adobe Technical Report, January 2008, disclose an image pickup apparatus that obtains the two-dimensional light intensity distribution and the angle information of the ray in the object space at the same time using “Light Field Photography”. The two-dimensional light intensity distribution and the angle information of the ray are collectively referred to as a light field, and three-dimensional information in the object space can be obtained by obtaining the light field. According to such an image pickup apparatus, the light field is obtained and an image processing is performed after taking an image so that a change of a focus position of the image which is called a refocus, a shot point of view, a depth of field, or the like can be performed.
Japanese Patent No. 4264569 discloses an image pickup apparatus that switches positions of a lens array in the configuration that is disclosed in Ren Ng, et al., “Light Field Photography with a Hand-held Plenoptic Camera”, Stanford Tech Report CTSR 2005-2 so that operations of taking a common image and obtaining the light field can be switched.
However, a harmful effect of a case where a position or a size of an exit pupil of an imaging optical system is changed and a measure for the harmful effect are not disclosed in Ren Ng, et al., “Light Field Photography with a Hand-held Plenoptic Camera”, Stanford Tech Report CTSR 2005-2, and Andrew Lumsdaine, et al., “Full Resolution Light Field Rendering”, Adobe Technical Report, January 2008. The exit pupil of the imaging optical system is changed by varying the magnification or focusing of the imaging optical system, or narrowing an aperture. When the exit pupil of the imaging optical system is changed, a light beam corresponding to a certain position on an object plane does not enter an appropriate region on an image pickup element. Therefore, the number of pixels which a ray does not enter, called a dead zone, are increased, and a phenomenon in which rays that have different positions and angles enter the same pixel on the object plane, called crosstalk, is generated. In addition, a sampling pitch related to angle information of the ray that is an angle component of a light field is increased. In this case, an image that is generated by the reconstruction described above is limited. For example, a refocus is performed by moving a focus position back and forth with reference to a focused object plane as an axis at the time of taking an image, and a movable range is decreased when the sampling pitch of the angle component of the light field is increased.
Japanese Patent No. 4264569 discloses an image pickup apparatus capable of varying a position of a lens array so as to obtain the light field. However, it is performed to switch a common operation of taking an image and an operation of obtaining the light field. It discloses neither the harmful effect of the case where the position or the size of the exit pupil of the imaging optical system is changed nor the measurement for the harmful effect. In addition, a way to the change of the interval between the lens array and the image pickup element and the variation of the exit pupil are not correlated to each other.